Retractor lens



M. BERTSCH RETRACTOR LENS April 18, 1961 Filed Sept. 9, 1955 PIP/0A HAT D R m m v! a n W m a JNVENTOR.

United States Patent RETRACTOR LENS Marguerite Bertsch, 3501-03 Hudson Blvd., Union City, NJ.

Filed Sept. 9, 1955, Ser. No. 533,299 1 Claim. (Cl. 95-1) The present application is for a patent on my invention, retractor lens.

Retractor lens is an invention presenting a new and unconventional method of lens construction, having definite advantages over the conventional lens used centrally, in the conventional manner. The advantages of the present invention will become more apparent from a consideration of the following explanation and description taken in conjunction with the appended drawings, in which Figure 1 is a schematic perspective view of a conventional centrally used lens and diaphragm useful in explaining principles of the present invention. Figure 2 is a greatly magnified view of the image point 2 of Figure 1.

Figure 3 is a wide-diameter lens cut into three sections A, B and C. Y

Figure 4 is the wide-diameter lens of Figure 3, with its three sections A, B and C separated.

Figure 5 is the left off-center section A of Figure 4, masked except for a central aperture, bending its imageproducing rays obliquely to the right.

Figure 6 is the right off-center section C of Figure 4, masked except for a central aperture, bending its imageproducing rays obliquely to the left.

Figure 7 is the central section B of the wide-diameter lens, masked except for a central aperture, focusing its image-producing rays in the conventional manner of the conventional lens used centrally.

Figure 8 is the left off-center section A of the widediameter lens, positioned over the right off-center section C, with the thick inner edge of section A directly over the thinner outer edge of section C.

Figure 9 is the lens combination of Figure 8 masked so that the combined left and right off-center sections, -A and C, of the wide-diameter lens can function only through a central aperture which, in manufacturing, will be the only part manufactured and used.

The basis for the present invention is my discovery of the advantages to be gained by the use of off-center lens sections in preference to conventional lenses ground and used centrally. While it is true that the oblique off-center rays must be eliminated as much as possible in a lens used centrally, a quite different effect can be expected when we get away from the center and use the oblique offcenter rays exclusively, as in the present invention, retractor lens.

How this operates will be made clear in the following description and drawings.

Referring to Figure 1, there is shown a lens 3 used centrally, in the conventional manner, that is with its central axis pointed toward the picture source of which the lens produces an image. Thus, if numeral 1 represents a point in the picture source or scene being photographed, this scene point 1 is the origin of a cone of light rays passing through as much of the lens 3 as is exposed by a conventional diaphragm 4 which may be interposed between the lens 3 and the scene point 1.

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This cone of light rays 5 will be brought to a focus by the lens 3 at some image point 2. The individual light rays thus focused, come from an infinity of directions entirely around the imaginary line joining the scene point 1 and the center of the lens 3, around a circumference of 360 degrees. However accurately these rays may impinge on a single image point 2, there is a stretching or distorting of the image point 2, individual to each of the rays, and this distortion or displacement of the points margin, by each individual ray, is in that rays own special direction.

This is illustrated in Figure 2, which shows an immensely enlarged view of the image point 2, showing it stretched or distorted into a halo of blurriness or distortion 6 around its entire circumference, because of the infinity of directions from which light rays were brought to a focus at the image point 2. The worst offenders, of course, are the more oblique rays, and the image is sharpened by reducing the size of the diaphragm aperture and thus eliminating the more oblique or fringe rays. However, the diaphragm aperture cannot be cut down beyond the point at which too little light passes through the lens for photographic purposes, and therefore the effect of the infinity of directions from which light is brought to a focus at each image point, when a lens is used centrally in this manner, cannot be entirely eliminated. This produces a halo 6 as shown in Figure 2, and the distortion around each image point, and the overlapping halos around contiguous image points, cause blurring or flatness of the complete image.

I have discovered that we can achieve greater clarity of image by cutting down to a minimum the number of directions from which light is brought to a focus in each of the image points. This is done by avoiding the use of a lens centrally, which is the conventional manner in which the lens 3 is used in Figure l.

How the conventional use of a lens centrally is avoided in the retractor lens, and what improvement we gain by using off-center lens sections, we will explain as follows.

To make clear the working principles of a retractor lens, I show in Figure 3 a wide-diameter lens 7 cut into three sections; a left off-center section A, a right offcenter section C and a central section B.

Figure 4 shows the three sections A, B and C of lens 7 separated after cutting.

Figure 5 shows the left off-center section A of widediameter lens 7 in Figure 4 covered by an opaque mask 8 except for a central functioning aperture 9, bending its image-producing rays 5 obliquelyto the right.

Figure 6 shows the right off-center section C of widediameter lens 7 in Figure 4 covered by an opaque mask 8 except for a central functioning aperture 9, bending its image-producing rays 5 obliquely to the left.

Figure 7 shows the central section B of the wide diameter lens 7 in Figure 4 covered by an opaque mask 8 except for a central functioning aperture 9 sending its image-producing rays 5 rearward from the lens, in the conventional manner of a lens used centrally.

While I have shown how sections B, A and C were derived as central and as left and right oifcenter sections respectively of wide-diameter lens 7, it is understood that, in manufacturing, only the functioning apertures 9 of these sections will be manufactured and used.

It is only with the functioning parts 9 of off-center sections A and C of Wide-diameter lens 7 that we are concerned in this invention. The functioning part 9 of section B of the lens 7 is used merely as a control since it is part of the same wide-diameter lens 7 used centrally, in the conventional manner, and the image it produces will show what improvement is accomplished by using sections A and C of wide-diameter lens 7 as a retractor lens.

The functioning part 9 of masked lens section A in Figure 5 bends its image-forming rays 5 to a focus in each point of the image, only horizontally to the right, indicated schematically by the bundle of light rays 5 in Figure 5 l The functioning part 9 of masked lens section C in Figure 6 bends its image-forming rays 5 to a focus in each point of the image, only horizontally to the left, indicated schematically by the bundle of light rays 5 in Figure 6.

Distortion of impingement, in such a lens structure, is essentially in one direction only. The image points brought to a focus by the left off-center wide-diameter lens section A, will be distorted only horizontally to the right. The image points brought to a focus by the right off-center wide-diameter lens section C, will be distorted only horizontally to the left.

Being unidirectional, such distortions can be readily counteracted or corrected. There is not required here, for correction, the elaborate costly negative and positive elements that are required to correct a lens used centrally with concomitant distortion due to the multiplicity of directions and angles of refraction from which light arrives at each of the image points. The unidirectional light from an off-center lens section is also homogeneous spherically and somewhat chromatically. To correct its left or right distortion, it is only necessary to retract the obliquity of the rays it bends to the left or right. Hence the name retractor lens.

Figure 8 shows how this is done. The retractor lens combination of Figure 8 is completely self-correcting. To retract the right obliquity of the image rays transmitted by section A of wide-diameter lens 7, it is necessary merely to lay upon section A section C of the same wide-diameter lens 7, as in Figure 8, crossing the sections so that the thick inner edges of one section lie over the thin outer edges of the other section and vice versa. A remarkably clear image is at once produced even without mask aperture or diaphragm. The image is thrown straight back of the retractor lens combination,

and the focal length of wide-diameter lens 7, as shown in its central section B, is cut in half by the retractor lens combination.

Figure 9 is the retractor lens combination of Figure 8 covered by an opaque mask 8 except for a central functioning aperture 9 exposing the central part of the retractor lens combination, which, in manufacturing, will be the only part manufactured and used.

The retractor lens has one half the focal length of the central section B of the wide-diameter lens 7. it is incomparably more clear and it is thoroughly corrected. It can be used at wide apertures that would be impossible with a centrally used lens.

Having thus described my invention, retractor lens, what I claim as original, and desire to secure by Letters Patent, is:

A corrected lens combination consisting of two paired off-center sections of a wide-diameter spherical lens, the paired sections being taken along the same diameter of the wide-diameter lens, at equal and opposite distances from the center, the two sections being superposed upon each other, in reverse, with the thinner outer edge of one section lying over the thicker inner edge of the other section, whereby the refraction of the one off-center lenssection, practically unidirectionally to one side, is 001m pletely reversed and corrected by the identical degree of practically unidirectional refraction of the other 16118? section in the opposite direction, the resulting image being sent straight rearward from the lens-combination, at half the focal length of the wide-diameter lens used centrally, the lens-combination being substantially no thicker at its center than the wide-diameter lens.

References Cited in the file of this patent UNITED STATES PATENTS 1,328,293 Parker Jan. 20, 1920 1,629,192 Winzenburg May 17, 1927 2,185,221 Nakken Jan. 2, 1940 

